Acids & Bases Overview
It is essential for students to know …
that substances can be classified as
acids, bases or neutral based on their
acids and bases are solutions usually
with water as the solvent.
Acids & Bases - pH
The pH scale is a way to measure how acidic
or basic a solution is.
The pH range of a solution is between 0 and
The pH of pure water is 7
◦ Any solution with a pH of 7 is neutral solution. It
is not an acid or a base.
The pH of an acidic solution is less than 7
◦ The lower the number, the more acidic the
The pH of a basic solution is greater than 7
◦ The higher the number, the more basic the
Acids & Bases - Acid
Acids can be identified by their…
sour taste (for example lemons and
oranges contain acids)
reaction with some metals such as
reaction with bases to form a neutral
pH solution (for example, vinegar
reacting with limestone).
Acids & Bases - Base
Bases can be identified by their…
bitter taste (for example, unsweetened
cocoa has a bitter taste)
by its slippery feel (for example, dish
by its reaction with acids to form a
neutral pH solution (for example, an
antacid to soothe an acid stomach).
Acids & Bases - Neutral
It is neither an acid nor a base (for
example, pure water is a neutral
solution and has a pH of ~7.0)
It is essential for students to know…
how to use indicators (including litmus
paper, phenolphthalein, and pH paper)
to determine the relative pH of a
Indicators are substances that can be
used to determine whether a solution
is acidic, basic, or neutral.
Indicators - Litmus paper
Has a special dye on it that changes
colors in the presence of an acid or
Blue litmus paper turns red in an
acid, and stays blue in a base.
Red litmus paper turns blue in a
base, and stays red in an acid.
Both red and blue litmus paper turn
violet in a solution that is neutral
(neither an acid nor a base).